JP4320902B2 - Metal cask lid sealing device for spent fuel transportation and storage - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a lid seal device for a spent metal transportation / storage metal cask used for storing and transporting or storing spent fuel after use in a nuclear power plant or the like.
[0002]
[Prior art]
Spent fuel generated at nuclear power plants must be stored in a tightly sealed container and stored strictly for a long period of time until the radioactive level drops below the reference value due to repeated natural decay. .
[0003]
When storing spent fuel, as shown in FIG. 2, conventionally, in a building 1 of a nuclear power plant, a cylindrical metal cask 3 with a top lid removed in a cask pit 2 is used. The spent fuel (aggregate) 6 collected in the spent fuel pit 5 is transferred by the fuel replacement device 7 into the cavity of the metal cask 3 in a vertically arranged state, and then in such a state. The metal cask 3 is transported to the cleaning pit 9 using the auxiliary building crane 8, and the spent fuel 6 is sealed in the metal cask 3 by fixing a lid to the upper end of the metal cask 3 with a bolt. To be included. Thereafter, the metal cask 3 is mounted sideways on a transport vehicle 12 that is kept waiting at the exit 11 of the building 1 and stored by sea transport by the transport ship 4 or by direct land transport by the transport vehicle 12. It is carried into the receiving area 10 of the facility and stored in the storage area 13.
[0004]
As shown in detail in FIG. 3 (a), the metal cask 3 is configured so that the upper end opening of a cylindrical cask cylinder 21 whose lower end is closed with a bottom plate 20 is covered with a primary lid 24 and a secondary lid 25 outside thereof. 3B, the primary lid 24 and the upper lid surface of the cask cylinder 21 and the secondary lid seal surface of the secondary lid 25 and the upper edge of the cask cylinder 21 are shown enlarged in FIG. The rubber O-rings 22 and 23 are sandwiched between the lids and the lid is sealed, and the primary lid 24 and the secondary lid 25 are attached to the peripheral portions thereof by bolts 32 and 33, respectively. Neutron shielding materials 26, 27, and 28 are disposed outside the bottom plate 20 and the secondary lid 25, respectively, and the outer sides of these neutron shielding materials 26, 27, and 28 are covered with an outer cylinder 29, a cover 30, and a cover 31. Configuration and And Aru. Reference numeral 34 denotes a trunnion used when the metal cask 3 is suspended by the auxiliary building crane 8.
[0005]
[Problems to be solved by the invention]
However, when the metal cask 3 is used for both transportation and storage of spent fuel, the secondary lid 25 is transported during transportation in order to obtain resilience against vibration load during transportation. The O-ring 23 is used for the sealing portion of the secondary lid 25. However, during storage, a metal gasket is used so as to ensure long-term sealing. It is necessary to replace the gasket from the O-ring 23 to a metal gasket. Therefore, when the metal cask 3 is used for storage, the secondary lid 25 is temporarily removed and a metal gasket is installed instead of the rubber O-ring 23. There is a problem that much labor is required because the opening and closing operation of the secondary lid 25 for attaching the secondary lid 25 must be performed.
[0006]
Therefore, the present invention can seal the secondary lid with the metal gasket without opening and closing the secondary lid of the metal cask when the metal cask is used for storage after the spent fuel is transported using the metal cask. It is something to try.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention allows spent fuel to be stored in a cylindrical cask cylinder whose lower end is closed, covers the upper end opening of the cask cylinder with a primary lid, and further covers the outer side thereof as a secondary. In the lid sealing device for spent fuel transport / storage combined metal cask, which is covered with a lid, and seals the inside of the cask cylinder by sealing the primary lid and the secondary lid to the upper end surface of the cask cylinder. Two sealing material fitting grooves are formed over the entire circumference on the sealing surface of the secondary lid in contact with the upper end surface of the spacer, and the spacer plate is detachably sandwiched in the secondary lid sealing portion outside the outer groove. A metal gasket is installed in the inner groove, and a rubber O-ring is installed in the outer groove to seal the secondary lid seal with the spacer plate sandwiched. Remove the spacer plate The metal gasket is a structure in which to be able to seal the secondary lid seal.
[0008]
When the spacer plate is sandwiched between the seal surface of the secondary lid and the secondary lid seal part of the upper end surface of the cask cylinder and the bolt is tightened, the metal gasket does not adhere to the upper end surface of the cask cylinder but only the O-ring adheres. In other words, the sealing performance can be ensured with an O-ring having a restoring property against the vibration load during transportation. On the other hand, when the spacer plate is removed and the bolt is tightened, the O-ring is further compressed and the metal gasket is brought into close contact with the upper end surface of the cask cylinder, thereby ensuring long-term sealing performance by the metal gasket. Will be.
[0009]
Further, by making the spacer plate made of rubber, the vibration load during transportation can be dispersed and received.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0011]
1 (a) and 1 (b) show an embodiment of the present invention. Like the metal cask 3 shown in FIG. 3, spent fuel is placed in a cylindrical cask cylinder 21 with its lower end closed. After the storage, the upper end opening of the cask cylinder 21 is covered with the primary lid 24 and the secondary lid 25, the seal portion between the upper end surface of the cask cylinder 21 and the primary lid 24, the upper end surface of the cask cylinder 21, and the secondary lid 25. The sealing surface of the secondary lid 25 facing the secondary lid sealing portion 14 between the secondary lid 25 and the upper end surface of the cask barrel 21 is configured so that the inside of the cask barrel 21 is sealed by sealing the sealing portion of the secondary lid 25. 25a, two grooves 15 and 17 for fitting the sealing material are formed over the entire circumference, the inner groove 15 is used as a metal gasket groove, and the metal gasket 16 is fitted and attached to the metal gasket groove 15, The outer groove 17 is used as an O-ring groove. A rubber O-ring 18 is fitted in the groove 17 for mounting, and a secondary lid is formed between the sealing surface 25a of the secondary lid 25 located outside the O-ring groove 17 and the upper end surface of the cask cylinder 21. A thin spacer plate 19 having a circumferentially divided structure is arranged in a ring shape and sandwiched between the seal portion 14 so that it can be attached and detached by tightening the bolts 33. The size is such that the seal portion 14 can be sealed while the spacer plate 19 is sandwiched. Other configurations are the same as those shown in FIG. 3, and the same parts are denoted by the same reference numerals.
[0012]
When transporting in a state where spent fuel is housed in the metal cask 3, as shown in FIG. 1 (a), the primary lid 24 is attached with bolts 32 so as to cover the upper end opening of the cask cylinder 21, and the cask cylinder. In a state where a rubber O-ring 22 is disposed and sealed between the inner peripheral side of the upper end surface of 21 and the primary lid 24, the metal gasket 16 is inserted into the metal gasket groove 15, and the O-ring groove. 17, the seal surface 25 a of the secondary lid 25 with the O-ring 18 attached thereto is opposed to the upper end surface of the cask cylinder 21, and the outer peripheral portion of the seal surface 25 a of the secondary lid 25 and the upper end surface of the cask cylinder 21 The secondary cover 25 is attached by tightening the bolts 33 with the spacer plate 19 sandwiched therebetween.
[0013]
With this state, the O-ring 18 is compressed by the secondary lid seal portion 14 between the secondary lid 25 and the upper end surface of the cask cylinder 25, and resists compression of the O-ring 18. The sealing force is obtained by the restoring force. At this time, a gap corresponding to the thickness of the spacer plate 19 is formed between the seal surface 25 a of the secondary lid 25 and the upper end surface of the cask cylinder 21, so that the metal gasket 16 is brought into close contact with the upper end surface of the cask cylinder 21. It will never be done. Therefore, the vibration load during transportation can be buffered and absorbed by the O-ring 18.
[0014]
When the metal cask 3 is transported in the above state and then stored as it is, the bolt 33 is loosened, the spacer plate 19 is removed, and then the bolt 33 is tightened again. As a result, as shown in FIG. 1B, the O-ring 18 is further compressed and the metal gasket 16 at the secondary lid seal portion between the seal surface 25a of the secondary lid 25 and the upper end surface of the cask cylinder 21. Is brought into close contact with the secondary lid 25 and the upper end surface of the cask cylinder 21. Therefore, even if the restoring property of the O-ring 18 deteriorates due to long-term use, the long-term integrity of the sealing performance can be maintained due to the presence of the metal gasket 15.
[0015]
As described above, in the present invention, after the metal cask 3 is transported, it can be switched to the seal with the metal gasket without opening and closing the secondary lid 25 when it is used for storage.
[0016]
The spacer plate 19 is used to form a gap between the metal gasket 16 and the upper end surface of the cask cylinder 21 during transportation. However, the spacer plate 19 is made of rubber, so that the vibration acting on the O-ring during transportation is used. It goes without saying that the load can be distributed and received, and various changes can be made without departing from the scope of the present invention.
[0017]
【The invention's effect】
As described above, according to the lid seal device for the spent fuel transportation / storage combined metal cask of the present invention, the spent fuel is stored in the cylindrical cask cylinder having the lower end closed, and the upper end of the cask cylinder is stored. Covering the opening with a primary lid, and further covering the outside with a secondary lid, and sealing the inside of the cask cylinder by sealing the primary lid and the secondary lid to the upper end surface of the cask cylinder In the storage and metal cask lid sealing device, two sealing material fitting grooves are formed on the sealing surface of the secondary lid that is in contact with the upper end surface of the cask cylinder, and the outer groove is located outside the outer groove. The spacer plate is detachably sandwiched between the secondary lid seal part, a metal gasket is mounted in the inner groove, and the secondary lid seal part is sealed with the spacer plate sandwiched in the outer groove. Rubber O-Li Since the metal gasket can seal the secondary lid seal when the spacer plate is removed, the seal surface of the secondary lid and the upper end surface of the cask cylinder are removed by attaching and detaching the spacer plate. The secondary lid seal part between the two can be switched to a metal gasket seal without opening and closing the secondary lid, and the sealability can be secured with an O-ring that is resilient to vibration loads during transportation. Because it can be easily performed in a state that can be sealed with a metal gasket with long-term soundness during storage, and the spacer plate is made of rubber, vibration during transportation An excellent effect is obtained such that the load can be distributed and received also on the spacer plate, which is advantageous.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 shows an embodiment of a metal cask lid sealing device for spent fuel transportation and storage according to the present invention, in which (a) is a partially enlarged sectional view showing a state during transportation, and (b) is storage. It is a partial expanded sectional view which shows the state of time.
FIG. 2 is a schematic diagram showing an example of a handling flow when storing spent fuel.
FIGS. 3A and 3B show an example of a metal cask, where FIG. 3A is a cut side view, and FIG. 3B is an enlarged view of a portion A of FIG.
[Explanation of symbols]
3 Metal cask 6 Spent fuel 14 Secondary lid seal 15 Metal gasket groove (seal material fitting groove)
16 Metal gasket 17 O-ring groove (sealing material fitting groove)
18 O-ring 19 Spacer plate 24 Primary lid 25 Secondary lid 25a Seal surface 32, 33 Bolt

Claims (2)

The spent fuel is stored in a cylindrical cask cylinder with the lower end closed, the upper end opening of the cask cylinder is covered with a primary lid, and the outer side is covered with a secondary lid. The primary lid and the secondary lid In the lid sealing device for the spent fuel transportation / storage combined metal cask that seals the inside of the cask cylinder by sealing the upper end face of the cask cylinder, the sealing surface of the secondary lid in contact with the upper end face of the cask cylinder Two sealing material fitting grooves are formed over the entire circumference, and a spacer plate is detachably sandwiched between the secondary lid seal portion outside the outer groove, and a metal gasket is provided in the inner groove. A rubber O-ring that can seal the secondary lid seal with the spacer plate sandwiched in the outer groove is attached. When the spacer plate is removed, the metal gasket becomes secondary. Cover the lid seal Spent fuel transportation and storage combined metal cask lid sealing apparatus characterized by having the structure to be Lumpur. The lid seal device for a metal cask used for both transportation and storage of spent fuel according to claim 1, wherein the spacer plate is made of rubber.

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